Diesel engines typically have higher thermal efficiency and lower fuel consumption rates than gasoline engines due to the increased compression ratio of the diesel combustion process and the higher energy density of diesel fuel. Consequently, diesel engines can have a higher thermal burn efficiency which can lead to improved fuel economy as compared to gasoline engines with similar output.
The development of diesel engines has become challenging in view of relatively stringent emission limits. One such challenge relates to limiting engine noise while attempting to improve fuel consumption and produce low levels of regulated emissions.